Electron discharge device



Sept. 5, 1933. V. BUSH ELECTRON DISCHARGE DEVICE Filied NOV. 24. 1922 2Sheets-Sheet 1 fivenzor:

I UarznvarBas/z Sept. 5, 1933.

v. BUSH 1,925,300

ELECTRON DISCHARGE DEVICE Filed Nov. 24. 1922 2 Sheets-Sheet 2 F 9&1 755 L/Hl I x: J H L ULQOMO lhven Z0 r: D0 2172 6220 r 23 as]:

Patented Sept. 5, 1933 PATENT; OFFICE ELECTRON DISCHARGE navrca VannevarBush, Medford, Mass., assignor to Raytheon, Inc., Cambridge, Mass., acorporation of Massachusetts Application November 24, 1922 Serial No.602,97!

7 Claims.

Owing to the high internal drop of the usual type of thermionic tube arelatively high potential between the cathode and anode is equired to.produce a substantial current flow, even though '5 the cathode isheated to incandescence, and the electrons therefore impinge upon theanode with high velocity. Consequently the efliciency of the tube isvery low and the anode heats excessively. For'example, to produce acurrent ofone-tenth 10 ampere a voltage of the order of 200 volts isusually required; and such a voltage causes the electrons to strike theanode with enormous speed. Inasmuch as the energy loss is the productofcurrent and potential drop in the tube it is evident that the loss ishigh for such small current flow. A thermionic tube requiring a highvoltage to drive current through it is relatively inefiicient whenemployed in a circuit of moderate voltage.

The principal object of the present invention is to produce a copiousflow of electrons between electrodes at a low or even zero internal dropand to control such flow for purposes of amplifying or rectifyingcurrents, generating high frequency oscillations, receiving radiomessages, converting heat into electrical energy, etc. Other objects areto increase the efiiciency of thermionic tubes and to decrease theheating of the anode.

In one aspect the invention consists in directing the electronicdischarge from the cathode to the region of the anode with an electricfield substantially independently of the potential difference betweenthecathode and anode so that little if any potential drop is requiredbetween the cathode and anode. The invention also consists indecelerating the electrons as they approach the anode, this preferablybeing effected with the same electric field employed in impelling theelectrons from the cathode. Thus the electric field acts first toaccelerate and then to decelerate the electrons, and also to control thecourse of the electrons.

Apparatus for producing an electronic discharge according to the presentinvention is characterized by means other than the anode for pro- 45ducing an electric field adapted both to impel the electrons from thecathode and also to direct the electrons to the region of the anode withlittle or no potential difference between the cathode and anode. Thefield producing means prefer- 50 ably comprises at least one primarycharged surface for impelling the electrons from the cathode and atleast one secondary charged surface for assisting in controlling thecourse of the electrons, the charged surfaces producing component fields55 which together form a resultant field adapted to impel and direct theelectrons as aforesaid. The arrangement of the charged surfaces is suchthat the electrons are decelerated as they approach the anode so thatthe electrons lodge upon the anode with negligible velocity.

In an elementary form my improved tube comprises a cathode, ananode, acharged primary electrode and a charged secondary surface, all in a gasfree space. The anode may take any suitable form, as for example that ofa block or plate. The primary electrode may be in the form of a wire orplate located between the cathode and anode. Thesecondary electrodepreferably comprises a plate located between the primary electrode andthe cathode. The tube may also be provided with additional auxiliaryelectrodes as will appear hereinafter.

For the purpose of illustration typical concrete embodiments of theinvention are shown in the accompanying drawings, in which,--

Fig. 1 is a longitudinal section of a thermionic tube according to thepresent invention, the cathode and anode and other interior electrodesbeing shown in elevation;

Fig. 2 is a central longitudinal section taken at right angles to thatof Fig. 1;

Fig. 3 is a transverse section on line 33 of Fig. 2;

Fig. 4 is a longitudinal central section of a modified tube;

Fig. 5 is a transverse section on line 5-5 of Fig. 4; and

Figs. 6 to 11 are diagrams illustrating typical applications of theinvention.

The particular embodiment of the invention shown in Figs. 1, 2 and 3comprises a glass tube T evacuated to a substantially perfect vacuum,the tube containing a cathode K in the form of an incandescent filament,an anode A in the form of a rectangular plate, a primary electrode P inthe form of a wire located between the cathode and anode, a secondaryelectrode S in the form of a narrow plate or strip located between thecathode and primary electrode, and auxiliary electrodes X in the form ofnarrow plates or strips located at opposite sides of the cathode K.

As shown in Fig. 2 the cathode and primary electrode are parallel toeach other and the anode and secondary electrode are disposed in planesparallel to each other and parallel to the cathode and primaryelectrode. The various electrodes may be supported in the glass tube inany suitable manner, the leading-in conductors serving as supports inthe illustrated embodiment. The cathode may be heated by battery H andthe primary electrode P is given a relatively high positive chargethrough the leading-in conductor 12. The auxiliary electrodes X may becharged through leading-in conductor :0. The leading-in wire s isconnected to the secondary electrode S for the purpose of impressing a'charge on this electrode if desired.

With the cathodeK heated to incandescence by battery H and a highpositive potential impressed upon primary electrode P current may becaused to flow in the output circuit with little or no potential dropbetween the cathode and anode, the positive charge on electrode Pdrawing electrons away from the cathode K and with the assistance ofsecondary electrode S causing the electrons to travel along pathsapproximately indicated by broken lines 0 in Fig. 3. If a negativecharge is impressed upon secondary electrode S through the leading-inwire s the electrons leaving the cathode are thereby restrained frommoxing directly toward the primary electrode P; and if no charge isimpressed upon the secondary electrode through the leading-in wire selectrons from the cathode will quickly establish a negative charge onthe secondary electrode suflicient to cause the electrons to travel inthe curved paths indicated in Fig. 3. After the electrons haveprogressed far enough to be traveling away from the primary electrodetheir momentum is relied upon to carry them the rest of the way to theanode. Thus the primary electrode P first accelerates the electrons andsubsequently decelerates them as they approach the anode. If the partsare properly co-ordinated and the strength of the field is properlyadjusted the electrons may be caused to lodge upon the anode withnegligible velocity, the electrons thus being transmitted from thecathode to the anode with little or no potential drop between thecathode and anode and producing little or no heating of the anode byvirtue of their deceleration before contact with the anode. The primaryelectrode P may be assisted in drawing electrons from the cathode byimpressing a positive charge upon the auxiliary electrode X, although itis to be understood that this is not necessary. With a tubesubstantially of the size and shape shown in Figs. 1, 2 and 3 a suitablepotential for the primary electrode P is 500 volts, although it will beunderstood that this will depend upon the purpose for which the tube isbeing used, etc.

Inasmuch as the electrons travel in curved paths and approach the anoderegion more or less tangentially to the anode it is sometimes desirable(although not essential especially if the electrostatic field,potentials and electrode spacings are properly co-ordinated) to provideone or more surfaces transverse of the paths of the electrons tointercept the electrons, thereby to prevent the electrons from passingtangentially past the anode. Such a surface is shown in Figs. 2 and 3 inthe form of a fin a fast to the anode in its central longitudinal plane.

The embodiment sh in Figs. 4 and 5 comprises an evacuated tube T', acoil filament cathode K, an anode A in the form of a cylinder having anelectron receiving surface in the form of a flange at the upper end ofthe cylinder, a primary electrode P in the form of a small disk abovethe mouth of the cylindrical anode, and a secondary electrode S in theform of a larger disk between the primary electrode and the cathode. InFig. 4 the battery for heating the cathode is indicated at H and thebattery for impressing high positive potential upon the primaryelectrode is indicated at B, the output circuit being designated O'-O.

Theoperation of the tube shown in Figs. 4 and 5 is similar to that ofthe tube shown in Figs. 1, 2 and 3, the cathode K being heated toincandescence and the primary electrode P' being charged with a positivepotential suflicient to impel electrons from the cathode to the anodealong paths which are approximately indicated by the roken ines 0'. Inthis tube no auxiliary electrodes corresponding to X in Figs. 1, 2 and 3are provided and the secondary electrode S is charged negatively by thebattery B which charges the primary electrode P positively.

In Fig. 6, which illustrates the application of the invention to a highpotential switch, D represents the high potential circuit which may beone of the three phases of a high voltage threephase transmission line,and E two branches in each of which is connected a thermionic tubecomprising a cathode K, an anode A, a primary electrode P, and asecondary electrode S, all according to the present invention, the tubesbeing inserted in the respective branches in reverse sense so thatelectrons flow from left to right in the upper tube and from right toleft 'in the lower tube. The cathodes are heated by batteries H, theheating I circuits being controlled by switches F. With the heatingcircuits closed and the positive potential impressed upon the primaryelectrodes P alternate cycles of current flow through the respectivetubes. However, when the switches F are opened current is interrupted bythe cooling of the cathodes. Inasmuch as the power flowing in theheating circuits is low no arcing results when the switches F are openedto interrupt the flow in the high potential circuit.

By regulating the tubes so that the maximum current flowing therein isless than the satura-' tion current the electrons arrive at the anodeswith low speed so that the anodes are heated very little. Since thespeed of the electrons depends merely on the net diiference ofelectrostatic potential between the cathode and anode and since theelectrons are impelled from the cathode to the anode with substantiallyno potential difference therebetween, the tube losses are small and thepresence of the tubes in the power circuit is ordinarily withoutsubstantial eifect upon the operation of the circuit. For example, ifthe working potential of the circuit is 110,000 volts the voltage dropacross each tube may be of the order of five volts or less.

In Fig. '7, which illustrates the application of the invention to arectifier system, K designates the cathode, A the anode, P the primaryelectrode, S the secondary electrode, H the cathode heating battery, Bthe battery for impressing a high positive potential upon the primaryelectrode P, G the source of alternating current, J the transformer, Lthe load which may comprise an electro-plating device and M a condenseracross the load L. From the foregoing it will be evident that thepositive charge on the primary electrode causes electrons to flow fromthe cathode to the anode, thereby permitting current to fiow in onedirection through the load circuit without permitting current to flow inthe reverse direction. The principal advantage of my improved tube insuch a circuit, or in any other rectifier circuit in which that thepotential drop from the cathode to the anode is always small when thecurrent is flowing, assuming that the load is adjusted so that themaximum, current drawn is less than the In Fig. 8, which illustrates theapplication of the unilateral conductivity may be made use of, is

the invention to an amplifying circuit, I represents the input circuit,0 the output circuit, K the cathode, A the anode, P the primaryelectrode, S the secondary electrode, H the cathode heating battery, Bthe high potential battery for charging the primary electrode, and B abattery for negatively charging the secondary electrode S. Variation ofthe potential on the primary and secondary electrodes produced byvariations in the current in the input circuit causes a variable currentto flow between'the cathode and anode thereby producing a variablecurrent in the output circuit having variations corresponding to thoseof the current in the input circuit. The secondary electrode S is alwaysmaintained negative by the batteries B and B so that it takes nocurrent. A battery Q of low potential may be connected in thecathode-anode circuit to bring the tube to the proper operating point inits characteristic. The potential of battery B should be so adjustedthat the current through the tube is somewhat less than saturationcurrent, whereby the variations in the potential of the secondaryelectrode S will cause wide variations in the current flowing betweenthe cathode and anode. Instead of varying the potential on the secondaryelectrode the input circuit may be connected to the primary electrode,although this arrangement is not usually desirable on account of thewider variations necessary in the input current in order to obtain thesame output current.

Fig. 9 illustrates a circuit connection for utilizing my improved tubefor producing high fre-' quency oscillations. In this figure K is thecathode, A the anode, P the primary electrode,

' S the secondary electrode, H the cathode heating battery, B thebattery for impressing a high positive potential on the primaryelectrode, J a coupler, R a condenser and U and U batteries of lowpotential. Oscillations in the circuit comprising R.- and J producesvariations in the potential on the secondary electrode S which variesthe current flow between the cathode and anode, and this in turnaugments the oscillations in the circuit R.J.

Fig. 10 shows a similar oscillator in which corresponding parts arecorrespondingly designated, the secondary electrode being connecteddirectly to the oscillation circuit R-J and the coil J being directlyconnected to the cathode. The advantage of these oscillators resides intheir high efiiciency as compared to the ordinary three electrode tube,this higher efiiciency resulting circuit.

One way oi. employing the invention in a radio receiving system is shownin Fig. 11 wherein the cathode K and anode A are connected to the anode.

example, current may be caused to flow -in the output circuit 0 merelyby heating the cathode K. While a high positive potential is impressedupon the primary electrode P no energy is drawn from the chargingbattery inasmuch as no current flows in this electrode.

From the foregoing it will be evident that the present invention afiordsa thermionic tube having a very low internal drop and having greatversatility.

I claim:

1. An electron discharge device operating without substantial ionizationcomprising a cathode, an anode, an additional electrode for drawingelectrons from the cathode, and electrostatic means for directing the.electrons away from said additional electrode to the region of theanode.

2. An electron discharge device operating without substantial ionizationcomprising an evacuated vessel containing a cathode, an anode, anelectrostatic electrode for impelling electrons from the cathode to theanode, and a shield for restraining the electrons from impinging uponsaid electrode.

3. An electric discharge device operating without substantial ionizationcomprising an evacuated vessel containing a cathode, an anode, a primaryelectrode for impelling-electrons from the cathode and a secondaryelectrode for directing the electrons to the anode region, said primaryand secondary electrodes being offset from the path of electrondischarge.

4. An electron discharge device operating with-' out substantialionization, comprising an evacuated envelope, a cathode and an anodespaced apart therein and means comprising a plurality of spacedadditional electrodes for causing the current from the cathode to theanode to be a substantially pure function of the change in potential ofone of the electrodes, said means preventing electrons from the cathodefrom going to any one of said additional electrodes.

5. An electron discharge device operating withan anode, electrostaticelectrode means independent of the anode for impelling electrons fromsaid cathode to the anode region along curved paths, said electrodemeans lying outside said paths, and separate electrostatic means forcontrolling the flow of electrons from the cathode to the anode. i

6. An electron discharge device operating without substantial ionizationcomprising a cathode, an anode, an electrostatically charged electrodeindependent of the anode for impelling electrons from said cathode tothe anode region, said impelling electrode having a small surfacetransverse to the electron flow, so arranged that electrons attractedfrom the cathode travel beyond said impelling electrodeby virtue oftheir inertia, and impinge upon said anode, and means for distorting theelectron paths so that substantially no electrons impinge upon saidimpelling electrode.

'7. An electron discharge device operating without substantialionization comprising a cathode and anode, an electrostatically chargedelectrode independent of the anode for impelling electrons from saidcathode to said anode, and electrostatic means for preventing electronsfrom impinging on said electrostatic electrode and for controlling theelectron flow from said cathode to said VANNEVAR BUSH.

